Supporting Information. Interface Engineering of Metal Oxides using Ammonium Anthracene in Inverted Organic Solar Cells

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1 Supporting Information Interface Engineering of Metal Oxides using Ammonium Anthracene in Inverted Organic Solar Cells Il Jeon, Sasa Zeljkovic, Kei Kondo, Michito Yoshizawa, and Yutaka Matsuo,# * : Department of Mechanical Engineering, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo , Japan : Department of Chemistry, Faculty of Sciences, University of Banja Luka, Mladena Stojanovica 2, 78 Banja Luka, Bosnia and Herzegovina : Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama , Japan #: Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 2326, China Corresponding author: Y. Matsuo matsuo@photon.t.u-tokyo.ac.jp Contents: 1. Experimental 2. PCE Evaluations 3. Energetics Analyses 4. Other Properties of AA 5. Fullerene Catching Ability 6. Device Stability S-1

2 1. Experimental Device Fabrication. For the reference device, ITO substrates with size mm2 and an active area of 3 3 mm2 with a sheet resistance of 6 Ω/square (Kuramoto Co., Ltd.) were sonicated in cleaning surfactant (Semi Clean, M-Lo), water, acetone and 2-isopropanol for 15 min each. The substrates were then dried with N2 gun. ITO substrates were exposed to UV/O3 for 3 min in order to remove any remaining organic impurities. Water solutions with anthracene concentration ranging from 2.5 mg ml-1 to 9 mg ml-1 were dropped on the active surface at 25 C for 2 min. The water solution was covering only active area without interfering with the contacts. After 2 minutes residual solution was blown with N2 and (in the case of ZnO treatment) rinsed with water, and then dried with N2 gun. In the case of ITO experiment was done without rinsing. ZnO sol gel films were prepared using the method reported by Heeger et al.1 The metal oxides were baked at 2 C before depositing the photoactive layer. For the photoactive layer deposition, PTB7 and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) were purchased from Luminescence Technology Corporation and used as received without further purification. A blend solution of PTB7 and PC71BM was prepared in a mixed solvent of chlorobenzene (99%, CB) and 1,8diiodoctane (DIO) at a 97:3 ratio. PTB7 (1 mg) and PC71BM (15 mg) were initially dissolved in CB inside a nitrogen glove box (.97 ml). The solution was left stirring overnight at 6 C. After 24 h, the corresponding amount of DIO (3 µl) was added. The new solution was stirred 1 h at 7 C. The solution of PTB7:PC71BM:DIO (8 nm) was spin-coated at 15 rpm for 6 s on ZnO layer to give approximately 1 nm. For the cathodes, Ag (1 nm) was deposited by vacuum thermal evaporation at the rate of.2 Å/s. Characterizations. Current-voltage (J V) characteristics were measured by software-controlled source meter (Keithley 24) in dark conditions and 1 sun AM 1.5G simulated sunlight irradiation (1 mw/cm2) using a solar simulator (EMS35AAA, Ushio Spax Inc.), which was calibrated using a silicon diode (BS-52BK, Bunkokeiki). Topography images were recorded using an AFM operating in tapping mode (SPI38N, SII). Shimadzu UV-315 was used for the UV-vis-NIR S-2

3 measurement. X-ray Diffraction (XRD; Rigaku Smartlab diffractometer) using Cu Kα radiation operating with a power of 9 kw (45 kv, 2 ma) was used. Core level photoemission measurements were performed by XPS (PerkinElmer, 54MC) using monochromatic Al Kα radiation. The XPS resolution was estimated to be 1 ev and the energy offset was calibrated using the surface C 1s peak. Valence band information and Fermi levels were measured by Riken Keiki PYS-A AC-2 and kelvin probe S spectroscopy in air (ESA), respectively. They were calibrated by Au before the measurement. The structure of the electron-only device was Al/ZnO-(surface treatment)/al. The mobility was determined by fitting the dark current to a model of a single-carrier space charge limited current, which is described by the equation: J =!! ε!ε! μ!!!!, where J is the current density, µ is the mobility, e is the permittivity of free space, e r is the relative permittivity of the material, L is the thickness of the active layer, and V is the effective voltage. The experimental dark current density J of both P3HT:PCBM and P3HT:mix-PCBM was measured under an applied voltage swept from to 5 V. 2,3 S-3

4 2. PCE Evaluations Power Conversion Efficiency (%) ITO/ZnO/rinsed AAs ITO/ZnO/non-rinsed AAs ITO/non-rinsed AAs ITO/rinsed AAs Concentration (mgml -1 ) Figure S1. PCE plots of ITO/ZnO/rinsed AAs-based device (red open squares), ITO/non-rinsed AAsbased device (red closed squares), ITO/ZnO/non-rinsed AAs-based device (blue closed circles), and ITO/rinsed AAs-based device (blue open circles), according to AA concentrations. Table S1. Photovoltaic parameters of ANTHs-applied devices and a reference device under one sun (AM1.5G illumination, 1 mw cm -2 ). Device System V OC (V) J SC (ma cm -2 ) FF R S (Ωcm 2 ) R SH (Ωcm 2 ) PCE (%) ITO/ZnO/rinsed AAs.6±. 8.89±.27.58± ±.12 ITO/ZnO/non-rinsed AAs P3HT ITO/rinsed AAs ITO/non-rinsed AAs.59± ±.18.53± ±.2 ITO/ZnO/rinsed AAs.76± ±.2.7± ±.21 PTB7 ITO/non-rinsed AAs.6±. 15.2±.18.63± ±.11 [Reference] ITO [Reference] ITO/ZnO P3HT PTB P3HT.6±.1 9.2±.2.52± ±.21 PTB7.73±.3 16.±.46.65± ±.15 S-4

5 Current Density (ma cm -2 ) Ref. ITO only ITO/non-rinsed AAs Ref. ZnO Light Ref. ZnO Dark ZnO-AAs Light ZnO-AAs Dark Applied Bias Voltage (V) Applied Bias Voltage (V) Figure S2. J-V curves of the ITO only devices and the ITO/rinsed AAs-based devices (left); and the ZnO reference devices and the ZnO/rinsed AAs devices (right) comprising the PTB7 system. S-5

6 3. Energetics Analyses + N O O N Cl E g = 2.69 ev! LUMO = 2.25 ev! HOMO = 4.94 ev! Figure S3. Chemical structure of the AA surface modifier with a calculated band gap (left), and Gaussian-calculated absolute energy levels of LUMO (middle) and HOMO (right). Figure S4. PYS data of a) ITO, b) water-rinsed and c) non-rinsed AA-treated ITO; d) ZnO, e) waterrinsed and f) non-rinsed AA-treated ZnO. S-6

7 4. Other Properties of AA Absorption (arbitrary unit) ZnO only ZnO/non-rinsed AAs Wavelength (nm) Figure S5. UV-vis spectra of a ZnO film and an AA-treated ZnO film External Quantum Efficiency (%) Device with ZnO Device with AA on ZnO Wavelength (nm) Figure S6. EQE spectra of P3HT:PCBM-based OSCs using ZnO (red) and AA on ZnO (black) S-7

8 Current Density (ma cm -2 ) 1 x x x x x 1 3 ZnO ZnO/rinsed AAs ZnO/non-rinsed AAs Applied Bias Voltage (V) Figure S7. J V curves of the electron-only devices for SCLC measurement and electron mobilities (µ) given as an inset with the unit (cm 2 V -1 s -1 ). Figure S8. Crystallography of anthracene derivatives where charged ends are to the left and bent polyaromatic groups are facing to the right. The crystal was grown slowly by evaporating a water solution at room temperature for 3 days (CCDC ). 4 S-8

9 a)! b)! Figure S9. XPS spectra of a) ITO/non-rinsed AAs and b) ITO/ZnO/rinsed AAs. 5. Fullerene Catching Ability Figure S1. AFM images and r.m.s. roughness values of a) glass/ito, b) glass/ito/non-rinsed AAs, c) glass/ito/zno, d) glass/ito/zno/rinsed AAs, e) glass/ito/p3ht:pcbm, f) glass/ito/non-rinsed AAs/P3HT:PCBM, g) glass/ito/zno/p3ht:pcbm, and h) glass/ito/zno/rinsed AAs/P3HT:PCBM. S-9

10 Figure S11. A graphical illustration of the ANTHs interacting with a metal oxide, ZnO and fullerene derivatives, PC 61 BM. S-1

11 6. Device Stability 1.8 Normalized PCE Device with ZnO Device with AA on ZnO Device with AA on ITO Days Figure S12. Stability test data of three P3HT:PCBM-based OSCs with ZnO, AA on ZnO, and AA on ITO in ambient conditions (ca. 25 C, 5% humidity) Supporting Reference (1) Kyaw, A. K.; Wang, D. H.; Gupta, V.; Zhang, J.; Chand, S.; Bazan, G. C.; Heeger, A. J. Efficient Solution-Processed Small-Molecule Solar Cells with Inverted Structure. Adv. Mater. 213, 25 (17), (2) Liao, H.-C.; Lee, C.-H.; Ho, Y.-C.; Jao, M.-H.; Tsai, C.-M.; Chuang, C.-M.; Shyue, J.-J.; Chen, Y.-F.; Su, W.-F. Diketopyrrolopyrrole-Based Oligomer Modified TiO 2 Nanorods for Air-Stable and All Solution Processed poly(3- hexylthiophene):tio 2 Bulk Heterojunction Inverted Solar Cell. J. Mater. Chem. 212, 22 (21), (3) Riad, A. S.; Mahmoud, S. A.; Ibrahim, A. A. Structural and DC Electrical Investigations of ZnO Thin Films Prepared by Spray Pyrolysis Technique. Phys. B Condens. Matter 21, 296 (4), (4) Kondo, K.; Suzuki, A.; Akita, M.; Yoshizawa, M. Micelle-like Molecular Capsules with Anthracene Shells as Photoactive Hosts. Angew. Chemie Int. Ed. 213, 52 (8), S-11